CN116931295A - Optical phase modulation device and preparation method thereof - Google Patents

Abstract

The application belongs to the technical field of optics, and relates to an optical phase modulation device and a preparation method thereof, wherein the optical phase modulation device comprises the following components: a substrate (10); a first waveguide core (12) disposed on the substrate (10); a second waveguide core (16) disposed in the upper cladding (17) above the first waveguide core (12), the first waveguide core (12) and the second waveguide core (16) having a variable gap (104) therebetween; the stress module is arranged on the upper cladding layer (17) above the gap (104), the upper cladding layer (17) is deformed through the deformation of the stress module, and the gap (104) between the first waveguide core (12) and the second waveguide core (16) is enlarged or reduced through the deformation of the upper cladding layer (17). According to the optical phase modulation device provided by the application, under the condition that a specific physical effect is not needed, the effective refractive index of the optical waveguide can be changed only by changing the distance between the first waveguide core (12) and the second waveguide core (16) through the stress module, so that the optical phase modulation is realized.

Description

Optical phase modulation device and preparation method thereof

Technical Field

The application belongs to the technical field of optics, and particularly relates to an optical phase modulation device and a preparation method thereof.

Background

An optical phase modulator is a basic device in integrated optics and has a wide range of applications, and it generally uses some physical effect (electro-optical effect, thermo-optical effect, elasto-optical effect, etc.) generated when a specific excitation (electric field, temperature or stress, etc.) is applied to an optical waveguide to cause a change in the effective refractive index of the optical waveguide, so as to change the phase of a light beam passing through the optical waveguide, thereby realizing optical phase modulation.

Current optical phase modulators are mostly based on some physical effect, and thus have specific requirements for the optical waveguide material properties and device structure, which inevitably create problems.

The existing scheme I is as follows: electro-optic phase modulation device

In the electro-optic phase modulation device, a signal electrode (S electrode) is arranged on an upper cladding right above a waveguide core, a grounding electrode (G electrode) is arranged on the upper cladding on two sides of the waveguide core, and the waveguide core is preferably made of a material with a high electro-optic coefficient.

And the electro-optic phase modulation device is used for realizing phase modulation by applying driving voltage to the S electrode so as to change the refractive index of the waveguide in an electric field generated by the S electrode and the G electrode.

It can be seen that an electro-optic phase modulation device based on the electro-optic effect in the existing scheme requires that the optical waveguide material has a higher electro-optic coefficient, and the existence of the electrode increases the optical loss.

The existing scheme II: thermo-optic phase modulation device

The thermo-optic phase modulation device is composed of a heater (thin film of metal, semiconductor, etc.) and an optical waveguide.

In the thermo-optic phase modulation device, a heater generates heat through electric current, so that the temperature of a waveguide (waveguide core and cladding) is increased, the (effective) refractive index is changed accordingly, and the optical phase modulation is realized.

Therefore, the thermo-optical phase modulation device based on the thermo-optical effect in the existing scheme II has the problems of high optical loss, power consumption and crosstalk.

The existing scheme III: stress optical phase modulation device

The stress optical phase modulation device consists of a piezoelectric capacitor (comprising upper and lower electrodes and a piezoelectric material (such as PZT) between the upper and lower electrodes) and an optical waveguide.

When voltage is applied to the upper electrode and the lower electrode of the piezoelectric capacitor, the piezoelectric material positioned between the upper electrode and the lower electrode of the piezoelectric capacitor generates strain (or stress) due to the inverse piezoelectric effect, the strain (or stress) change is caused to the waveguide core and the surrounding cladding, and the refractive index of the waveguide core and the surrounding cladding also changes due to the elastic optical effect, so that the optical phase modulation is realized.

As can be seen, the stress optical phase modulator based on the elasto-optical effect in the existing scheme is generally larger in device size, which is unfavorable for high-density integration.

In summary, the drawbacks of the prior art are as follows:

1. based on specific physical effects, the waveguide core is required to have higher characteristics corresponding to the effects, and the waveguide material is limited, such as an electro-optic phase modulation device;

2. in order to achieve higher modulation efficiency and modulation frequency, the electrode is required to be close to the waveguide core, and higher optical loss, such as an electro-optical phase modulation device and a thermo-optical phase modulation device, can be introduced;

3. the modulation efficiency is low, so that the device size is large, and high-density integration such as a stress optical phase modulation device is not facilitated.

Disclosure of Invention

The application aims to provide an optical phase modulation device structure and a preparation method thereof for realizing optical phase modulation.

According to a first aspect of an embodiment of the present application, there is provided an optical phase modulation device including:

a substrate;

a first waveguide core disposed on the substrate;

the second waveguide core is arranged in the upper cladding above the first waveguide core, and a variable gap is arranged between the first waveguide core and the second waveguide core;

the stress module is arranged on the upper cladding above the gap, the upper cladding is deformed through deformation of the stress module, and the gap between the first waveguide core and the second waveguide core is enlarged or reduced through deformation of the upper cladding.

Further, the upper cladding is formed into a cantilever beam or cantilever plate structure with one end fixed and the other end suspended;

the second waveguide core is formed in the suspended upper cladding layer, or at least a portion of the second waveguide core is formed in the suspended upper cladding layer.

Further, the optical phase modulation device further includes:

a thermal oxide layer disposed on the substrate;

the first intermediate layer is arranged on the thermal oxidation layer and coats the first waveguide core;

wherein the refractive index of the first waveguide core is higher than the refractive index of the thermal oxide layer and higher than the refractive index of the first intermediate layer.

Further, the optical phase modulation device further includes:

a second intermediate layer, a part of which is formed on the thermal oxide layer or the first intermediate layer and is formed into a cantilever beam or cantilever plate structure with one end fixed and the other end suspended, so that a second waveguide core is formed on the second intermediate layer;

wherein the refractive index of the second waveguide core is higher than the refractive index of the upper cladding layer and higher than the refractive index of the second intermediate layer.

Further, the stress module includes:

a lower electrode;

a piezoelectric layer disposed on the lower electrode;

an upper electrode disposed on the piezoelectric layer;

the voltage difference applied to the lower electrode and the upper electrode enables the piezoelectric layer to deform, the upper cladding layer is enabled to deform through the deformation of the piezoelectric layer, and the gap between the first waveguide core and the second waveguide core is enabled to be larger or smaller through the deformation of the upper cladding layer.

Further, the stress module further includes:

a dielectric layer coating the upper electrode, the piezoelectric layer and the lower electrode; the dielectric layer is provided with a first contact hole and a second contact hole; the first contact hole is used for partially exposing the lower electrode; the second contact hole is used for partially exposing the upper electrode;

a first buffer layer disposed between the lower electrode and the piezoelectric layer;

a second buffer layer disposed between the piezoelectric layer and the upper electrode;

and an adhesive layer disposed between the upper cladding layer and the first buffer layer.

Further, the stress module includes:

at least one thermal expansion layer sequentially arranged on the upper cladding layer;

a heater disposed on the thermal expansion layer;

wherein the coefficient of expansion of the thermal expansion layer is greater than the coefficient of expansion of the upper cladding layer, and the coefficient of expansion of the thermal expansion layer closer to the heater is greater than the coefficient of expansion of the thermal expansion layer farther from the heater; the heater heats the thermally-expansive layer such that the thermally-expansive layer is thermally-expansive-deformed, thereby changing the size of the gap between the first waveguide core and the second waveguide core.

Further, the first waveguide core and the second waveguide core are of a double-strip optical waveguide structure; the second waveguide core is positioned right above the first waveguide core;

the widths of the first waveguide core and the second waveguide core are smaller than the width of the gap; the width of the first waveguide core and the width of the second waveguide core are the same or different;

the thickness of the first waveguide core is the same as or different from the thickness of the second waveguide core;

the material of the first waveguide core and the material of the second waveguide core are the same or different.

Another aspect of the present application provides a method for manufacturing an optical phase modulation device, including:

providing a substrate;

forming a first waveguide core on a substrate;

depositing and patterning a sacrificial layer above the first waveguide core, wherein the width of the patterned sacrificial layer is larger than that of the first waveguide core below;

forming a second waveguide core on the sacrificial layer; the width of the second waveguide core is smaller than the width of the patterned sacrificial layer;

forming an upper cladding layer on the second waveguide core;

forming a stress module on the upper cladding layer;

etching to remove the sacrificial layer so as to form a variable gap between the first waveguide core and the second waveguide core;

the upper cladding layer is deformed through deformation of the stress module, and a gap between the first waveguide core and the second waveguide core is enlarged or reduced through deformation of the upper cladding layer.

Further, forming a first waveguide core on the substrate specifically includes:

depositing a thermal oxide layer on a substrate;

forming a first waveguide core on the thermal oxide layer;

depositing a sacrificial layer on the first waveguide layer, specifically comprising:

depositing a first intermediate layer on the thermal oxide layer formed with the first waveguide core, wherein the thickness of the first intermediate layer is greater than that of the first waveguide core, so that the first intermediate layer coats the first waveguide core;

depositing a sacrificial layer on the first intermediate layer;

wherein the refractive index of the first waveguide core is higher than the refractive index of the thermal oxide layer and higher than the refractive index of the first intermediate layer.

Further, forming a second waveguide core on the sacrificial layer specifically includes:

depositing a second intermediate layer on the first intermediate layer on which the sacrificial layer is formed;

forming a second waveguide core on the second intermediate layer; the second waveguide core is formed above the sacrificial layer, or at least a portion of the second waveguide core is formed above the sacrificial layer;

wherein the refractive index of the second waveguide core is higher than the refractive index of the upper cladding layer and higher than the refractive index of the second intermediate layer.

Further, the method comprises the steps of:

depositing and patterning a lower electrode metal layer on the upper cladding layer to form a lower electrode;

and depositing a piezoelectric material layer on the lower electrode, depositing an upper electrode metal layer on the piezoelectric material layer, and patterning the piezoelectric material layer and the upper electrode metal layer to form the piezoelectric layer and the upper electrode, so that the stress module formed after patterning partially covers the sacrificial layer in the width direction and is positioned in the range of the sacrificial layer in the length direction.

Further, before forming the lower electrode, it further includes: depositing an adhesion layer on the upper cladding layer; then, forming the lower electrode specifically includes:

depositing a lower electrode metal layer on the adhesion layer and patterning to form a lower electrode;

after forming the lower electrode, further comprising: depositing a first buffer layer on the lower electrode; then, a piezoelectric layer and an upper electrode are formed, specifically including:

depositing a piezoelectric material layer on the first buffer layer, depositing a second buffer layer on the piezoelectric material layer, depositing an upper electrode metal layer on the second buffer layer, and patterning the piezoelectric material layer, the second buffer layer and the upper electrode metal layer to form a piezoelectric layer and an upper electrode;

after forming the upper electrode, further comprising:

depositing a dielectric layer over the lower electrode, the upper electrode, and the upper cladding layer;

patterning the dielectric layer to form a first contact hole to partially expose the lower electrode and a second contact hole to partially expose the upper electrode;

and depositing and patterning a metal layer on the dielectric layer, and forming electrode leads of the stress module at the first contact hole and the second contact hole respectively.

Further, etching to remove the sacrificial layer includes:

forming a groove above the sacrificial layer to expose a part of the sacrificial layer;

and etching to remove the sacrificial layer through the groove to form a gap.

Further, forming a stress module, comprising:

forming at least one thermal expansion layer on the upper cladding layer;

forming a heater on the thermal expansion layer;

wherein the coefficient of expansion of the thermal expansion layer is greater than the coefficient of expansion of the upper cladding layer, and the coefficient of expansion of the thermal expansion layer closer to the heater is greater than the coefficient of expansion of the thermal expansion layer farther from the heater; the heater heats the thermally-expansive layer such that the thermally-expansive layer is thermally-expansive-deformed, thereby changing the size of the gap between the first waveguide core and the second waveguide core.

The technical scheme of the application has at least the following beneficial technical effects:

according to the optical phase modulation device provided by the application, the air gap is formed between the first waveguide core and the second waveguide core, and the effective refractive index of the optical waveguide can be changed only by changing the distance between the first waveguide core and the second waveguide core through the stress module under the condition that a specific physical effect is not needed, so that the optical phase modulation is realized.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the drawings required for the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to the drawings without inventive effort for those skilled in the art.

Fig. 1 is a schematic diagram of an optical phase modulation device in an exemplary embodiment of the present application;

fig. 2 is a schematic diagram of an optical phase modulation device according to another exemplary embodiment of the present application;

FIG. 3 is a top view of a first waveguide core and a second waveguide core in positional relationship with a first stress module formed in an exemplary embodiment of the application;

FIG. 4 is a top view of a first waveguide core and a second waveguide core in positional relationship with a first stress module formed in accordance with yet another exemplary embodiment of the present application;

fig. 5 is a flowchart of a method of fabricating an optical phase modulation device according to an exemplary embodiment of the present application;

FIG. 6 is a schematic diagram of a structure for forming a thermal oxide layer in an exemplary embodiment of the application;

FIG. 7 is a schematic diagram of a structure for forming a first waveguide core in an exemplary embodiment of the present application;

fig. 8 is a schematic view of a structure for forming a first intermediate layer in an exemplary embodiment of the present application;

FIG. 9 is a schematic diagram of a structure for forming a sacrificial layer in an exemplary embodiment of the application;

fig. 10 is a schematic view of a structure for forming a second intermediate layer in an exemplary embodiment of the present application;

FIG. 11 is a schematic diagram of a structure for forming a second waveguide core in an exemplary embodiment of the present application;

FIG. 12 is a schematic diagram of a structure for forming an upper cladding layer in an exemplary embodiment of the application;

fig. 13 is a schematic view of a structure for forming a second stress module in an exemplary embodiment of the application.

Wherein, the correspondence between the reference numerals and the component names in fig. 1 to 13 is:

10. a substrate; 11. a thermal oxide layer; 12. a first waveguide core; 13. a first intermediate layer; 14. a sacrificial layer; 15. a second intermediate layer; 16. a second waveguide core; 17. an upper cladding layer;

2. a stress module; 20. an adhesive layer; 21. a lower electrode; 22. a first buffer layer; 23. a piezoelectric layer; 24. a second buffer layer; 25. an upper electrode; 26. a dielectric layer; 27. a protective layer; 202. a first contact hole; 204. a second contact hole; 206. an electrode lead; 104; a void.

Detailed Description

The objects, technical solutions and advantages of the present application will become more apparent by the following detailed description of the present application with reference to the accompanying drawings. It should be understood that the description is only illustrative and is not intended to limit the scope of the application. In addition, in the following description, descriptions of well-known structures and techniques are omitted so as not to unnecessarily obscure the present application.

A layer structure schematic diagram according to an embodiment of the present application is shown in the drawings. The figures are not drawn to scale, wherein certain details may be exaggerated and some details may be omitted for clarity. The shapes of the various regions, layers and relative sizes, positional relationships between them shown in the drawings are merely exemplary, may in practice deviate due to manufacturing tolerances or technical limitations, and one skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions as actually required.

It will be apparent that the described embodiments are some, but not all, embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

In the description of the present application, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In addition, the technical features of the different embodiments of the present application described below may be combined with each other as long as they do not collide with each other.

The principle of the application:

most of the existing integrated optical phase modulators are based on specific physical effects (electro-optical effect, thermo-optical effect, elasto-optical effect and the like), the optical phase is modulated by changing the refractive index of waveguide materials (waveguide core and cladding), and certain limitation is imposed on selection of waveguide core materials.

The inventors found that: based on the double-strip waveguide structure, the effective refractive index of the waveguide is changed by changing the interval between the two waveguide cores, so that the optical phase modulation is realized, the specific physical effect is not based, and the limitation on the waveguide core material is small.

In the actual design process, the present inventors also found that: the effective refractive index of the double-strip optical waveguide is sensitive to the distance between the two waveguide cores, so that the double-strip optical waveguide has high modulation efficiency and is beneficial to realizing high-density integration of an optical phase modulation device.

The structure of the optical phase modulation device and the preparation method thereof provided by the embodiment of the application are described in detail below through specific embodiments and application scenes thereof with reference to the accompanying drawings.

Embodiment one:

in this embodiment, as shown in fig. 1, there is provided an optical phase modulation device including:

a substrate 10; a first waveguide core 12 disposed on the substrate 10; a second waveguide core 16 disposed above the first waveguide core 12, the first waveguide core 12 and the second waveguide core 16 having a variable gap 104 therebetween; wherein a variable gap 104 is left between the first waveguide core 12 and the second waveguide core 16, and the stress module 2 disposed on the upper cladding 17 above the gap 104 changes the distance between the first waveguide core 12 and the second waveguide core 16 by its own deformation. The effective refractive index of the optical waveguide can be changed by changing the spacing of the first waveguide core 12 from the second waveguide core 16 only by the stress module 2 without the need to rely on specific physical effects, thereby achieving optical phase modulation.

In this embodiment, the material of the substrate 10 may be silicon.

In this embodiment, the upper cladding 17 is formed into a cantilever beam (plate) structure with one end fixed and the other end suspended; the second waveguide core 16 is formed in the suspended upper cladding layer 17, or at least a portion of the second waveguide core 16 is formed in the suspended upper cladding layer 17. The distance between the cantilever (slab) structures is adjusted by the stress module 2, thereby changing the size of the gap 104 between the second waveguide core 16 and the first waveguide core 12.

Embodiment two:

in this embodiment, an optical phase modulation device is provided: the device consists of a substrate, a thermal oxide layer, a cantilever beam (plate) structure, a double-strip waveguide structure and a stress module. As shown in fig. 2, the optical phase modulation device specifically includes:

substrate 10, the material of substrate 10 may be silicon or other substrate material.

A thermal oxide layer 11 disposed on the substrate 10, wherein when the substrate 10 is made of a silicon material, a silicon oxide lower cladding layer (i.e., the thermal oxide layer 11) may be formed by a thermal oxidation process, and when the substrate 10 is made of other materials, the thermal oxide layer 11 may be a silicon oxide lower cladding layer or other cladding materials; the thickness of the thermal oxide layer 11 may be 1 to 10 μm.

The cantilever beam (plate) structure formed by the first intermediate layer 13, the second intermediate layer 15 and the upper cladding layer 17 together, wherein the materials of the first intermediate layer 13, the second intermediate layer 15 and the upper cladding layer 17 can be silicon dioxide or other cladding materials; one end of the cantilever beam (plate) structure is fixed on the thermal oxide layer 11, and the other end is suspended in the air; the thickness of the second intermediate layer 15 may be 0.02 to 0.2 μm.

The double-strip waveguide structure is composed of a first waveguide core 12 and a second waveguide core 16, a suspending part of a cantilever beam (plate) structure is arranged between the double-strip waveguides, and a gap 104 between the double-strip waveguides is a size-adjustable gap; the second waveguide core 16 is connected to the substrate 10 through the upper cladding 17 or the second intermediate layer 15, and an air gap may be formed between the second waveguide core 16 and the first waveguide core 12 in the whole process, or may be formed between the second waveguide core 16 and the first waveguide core 12, or may be formed between the second waveguide core and the first waveguide core.

The materials of the first waveguide core 12 and the second waveguide core 16 may be silicon nitride or other waveguide materials, and the refractive index of the first waveguide core 12 is higher than the refractive index of the first intermediate layer 13, and the refractive index of the second waveguide core 16 is higher than the refractive index of the second intermediate layer 15; preferably, the second waveguide core 16 may be located directly above the first waveguide core 12; preferably, the first waveguide core 12 and the second waveguide core 16 have the same width; preferably, the first waveguide core 12 and the second waveguide core 16 are the same thickness; preferably, the thickness of the first intermediate layer 13 is greater than the thickness of the first waveguide core 12, and the first waveguide core 12 is clad with the first intermediate layer 13.

The stress module 2 is arranged on the cantilever beam (plate) structure, the upper cladding 17 is driven to deform through the deformation of the stress module 2, and then the position of the second waveguide core is changed through the deformation of the upper cladding 17, so that the gap 104 is changed; the effective refractive index of the double-strip waveguide is sensitive to the distance between the two waveguide cores, and the size of the gap 104 is adjusted through the stress module 2, so that the double-strip waveguide has high modulation efficiency and is beneficial to realizing high-density integration of an optical phase modulation device.

In addition, considering the process implementation, the first intermediate layer 13 is used for wrapping the first waveguide core 12, so that the surface of the first waveguide core 12 is not damaged in the processing process, and the transition effect can be realized when light is transmitted in the waveguide core, so that the light is prevented from being directly dissipated into the air; similarly, the second intermediate layer 15 and the upper cladding layer 17 are used for wrapping the second waveguide core 16, so that the surface of the second waveguide core 16 is not damaged and prevented from dissipating light in the processing process, the processing difficulty is overcome, and the second intermediate layer 15 is used for avoiding the situation that the phase modulation caused by the sliding or unexpected displacement of the second waveguide core 16 is not expected because the second waveguide core 16 is partially or completely suspended above the first waveguide core 12.

Preferably, the stress module 2 may be designed as a piezoelectric actuator structure, and the piezoelectric material characteristic is utilized to drive the cantilever beam (plate) structure to deform, as shown in fig. 2, and the piezoelectric actuator is specifically:

the adhesion layer 20 may be selected according to the material or characteristics of the upper cladding layer 17 or the lower electrode 21, and is used for adhering the upper cladding layer 17 and the lower electrode 21 made of a metal material, and may be an unnecessary film layer of the piezoelectric actuator, and the thickness thereof may be determined according to the characteristics of the piezoelectric material;

the lower electrode 21, the lower electrode 21 is a metal layer, the material of which can be determined according to the characteristics of the piezoelectric material, is a necessary film layer of the piezoelectric actuator, and the thickness of which can be determined according to the design parameters of the piezoelectric actuator;

the first buffer layer 22 is an unnecessary film layer of the piezoelectric actuator, and the material of the first buffer layer can be determined according to the characteristics of the piezoelectric material, so that the first buffer layer plays a role in buffering in the deformation process of the piezoelectric actuator, and has better crystal orientation, piezoelectric characteristics and anti-fatigue characteristics for the piezoelectric material;

the piezoelectric layer 23 may be a common piezoelectric material, and is a necessary film layer of the piezoelectric actuator, and its thickness may be determined according to the design parameters of the piezoelectric actuator;

the second buffer layer 24 is an unnecessary film layer of the piezoelectric actuator, and the material of the second buffer layer can be determined according to the characteristics of the piezoelectric material, so that the second buffer layer plays a role in buffering in the deformation process of the piezoelectric actuator, and has better crystal orientation, piezoelectric characteristics and anti-fatigue characteristics for the piezoelectric material;

the upper electrode 25, the upper electrode 25 is a metal layer, the material of which can be determined according to the characteristics of the piezoelectric material, is a necessary film layer of the piezoelectric actuator, and the thickness of which can be determined according to the design parameters of the piezoelectric actuator;

the dielectric layer 26 may be silicon dioxide or other insulating materials, and the dielectric layer 26 is provided with a first contact hole 202 exposing the lower electrode 21 and a second contact hole 204 exposing the upper electrode 25, and the thickness of the dielectric layer may be determined according to practical design parameters or processes;

electrode leads 206, which are made of metal material, formed at the first contact holes 202 and the second contact holes 204, respectively;

the protective layer 27 may be silicon dioxide or other insulating material.

In order to facilitate the deformation of the cantilever (plate) structure, at least a portion of the piezoelectric actuator is disposed above the suspended portion in the cantilever (plate) structure, as shown in fig. 3 or fig. 4, in a top view, the piezoelectric layer 23, the second buffer layer 24 (including, for example), the upper electrode 25, and the first buffer layer 22 (including, for example) in the piezoelectric actuator should cover the suspended portion (the sacrificial layer in the processing process) in width and should be located in the range of the suspended portion (the sacrificial layer in the processing process) in length, and the film layers other than the above may be determined according to actual design parameters or processes, so as to improve the device integration.

Preferably, the stress module 2 may be further designed as a thermal expansion structure, and the expansion phenomenon is utilized to drive the cantilever beam structure to deform, so as to deform the upper cladding 17, and further change the position of the second waveguide core 16 relative to the first waveguide core 12, namely, change the gap 104; the size of the gap 104 is adjusted by the expansion structure, which is beneficial to realizing high-density integration of the optical phase modulation device.

Specifically, at least a thermal expansion layer is formed on the upper cladding layer 17, and then a heater is formed on the thermal expansion layer; wherein the coefficient of expansion of the thermal expansion layer is greater than the coefficient of expansion of the upper cladding layer, and the coefficient of expansion of the thermal expansion layer closer to the heater is greater than the coefficient of expansion of the thermal expansion layer farther from the heater; the heater heats the thermally-expansive layer, causing the thermally-expansive layer to thermally expand and deform, thereby changing the size of the void 104 between the first waveguide core 12 and the second waveguide core 16.

Preferably, in order to precisely control the modulation efficiency, it should be avoided that the second waveguide 16 is also subjected to heat to cause local expansion, so that a thermal insulation layer may be formed between the upper cladding 17 and the thermal expansion layer to avoid heat of the heater from being transferred to the second waveguide core 16;

in addition, a heat insulating layer is formed above or around the heater, namely between the heater and the dielectric layer 26, so that on one hand, heat outflow is avoided, the self control efficiency of the stress module 2 is ensured, and on the other hand, the influence of heat generated by the heater on the service lives of the dielectric layer 26, the protective layer 27 and the like is reduced.

FIG. 3 is a top view of a first waveguide core and a second waveguide core in positional relationship with a first stress module formed in an exemplary embodiment of the application; for a clearer illustration of the positional relationship of the stress module 2 to the first waveguide core 12 and the second waveguide core 16, fig. 3 shows a top perspective view, wherein the stress module 2 covers both the relatively fixed end of the upper cladding 17 and the suspended end of the upper cladding, i.e. a portion of the stress module 2 is located above the first waveguide core 12 and the second waveguide core 16.

Fig. 4 is a top view showing a positional relationship between a first stress module and a first waveguide core, and a second waveguide core according to another exemplary embodiment of the present application, and fig. 4 is a top perspective view, where the stress module 2 covers only one end of the upper cladding 17 that is suspended, that is, the stress module 2 is located entirely above the first waveguide core 12 and the second waveguide core 16.

Example IV

Another aspect of the present application provides a method for manufacturing an optical phase modulation device, such as the method flowchart shown in fig. 5.

In a preferred embodiment of the present application, a method for manufacturing an optical phase modulation device includes:

s1, providing a silicon substrate 10;

s2, as shown in FIG. 6, forming a silicon dioxide thermal oxidation layer 11 on a substrate 10 through a thermal oxidation process, wherein the thickness of the thermal oxidation layer 11 is 1-10 mu m;

s3, as shown in FIG. 7, a first waveguide core layer is deposited on the thermal oxide layer 11, and the first waveguide core layer is patterned to form a first waveguide core 12, where the material of the first waveguide core 12 may be silicon nitride or other waveguide materials.

S4, as shown in FIG. 8, depositing a first intermediate layer 13 on the thermal oxide layer 11 formed with the first waveguide core 12, wherein the material of the first intermediate layer 13 may be silicon dioxide or other cladding materials; the thickness of the first intermediate layer 13 is greater than the thickness of the first waveguide core 12; the refractive index of the first waveguide core 12 is higher than that of the thermal oxide layer 11 and higher than that of the first intermediate layer 13, and the thickness and width thereof are set according to the wavelength of light and the optical characteristics of the waveguide core material.

Planarizing the first intermediate layer 13; a first intermediate layer 13 of 0.02-0.2 μm is reserved above the planarized first waveguide core 12;

s5, as shown in FIG. 9, a sacrificial layer 14 is deposited and patterned on a partial area above the first intermediate layer 13, and the first waveguide core 12 is positioned in a range right below the patterned sacrificial layer 14, and the width of the patterned sacrificial layer 14 is larger than that of the first waveguide core 12 below; the material of the sacrificial layer 14 has a high wet etching selectivity ratio to silicon dioxide, such as metal; the thickness of the sacrificial layer 14 is 0.1 to 0.5 μm.

S6, as shown in FIG. 10, depositing a second intermediate layer 15 on the first intermediate layer 13 formed with the sacrificial layer 14; the material of the second intermediate layer 15 may be silica or other cladding material, and the thickness may be 0.02-0.2 μm.

S7, as shown in FIG. 11, depositing a second waveguide core layer on the second intermediate layer 15, and patterning to form a second waveguide core 16; the second waveguide core 16 is located directly above the first waveguide core 12, or at least a portion of the second waveguide core 16 is formed above the sacrificial layer 14; the material of the second waveguide core layer may be silicon nitride or other waveguide material. The refractive index of the second waveguide core layer is higher than that of the upper cladding layer 17 and higher than that of the second intermediate layer 15, and the material, thickness, and width of the second waveguide core 16 may be different from those of the first waveguide core 12; preferably the second waveguide core 16 has a width less than the width of the sacrificial layer 14.

S8, as shown in FIG. 12, depositing an upper cladding layer 17 on the second intermediate layer 15 formed with the second waveguide core 16;

planarizing the upper cladding layer 17; the material of the upper cladding layer 17 is silica, and its thickness is 1 to 10 μm.

S9. as shown in fig. 13, the stress module 2 is formed on the upper cladding 17: the method comprises the following specific steps:

depositing an adhesion layer 20 on the upper cladding layer 17;

depositing and patterning a lower electrode metal layer on the adhesion layer 20 to form a lower electrode 21; the lower electrode 21 is a metal layer, the material of which can be determined according to the characteristics of the piezoelectric material, and is an essential film layer of the piezoelectric actuator, and the thickness of which can be determined according to the design parameters of the piezoelectric actuator.

Depositing a first buffer layer 22 on the lower electrode 21; the first buffer layer 22 is an unnecessary film layer of the piezoelectric actuator, and its material may be determined according to the characteristics of the piezoelectric material.

Depositing a layer of piezoelectric material on the first buffer layer 22; depositing a second buffer layer 24 on the layer of piezoelectric material; is an unnecessary film layer of the piezoelectric actuator, and the material of the film layer can be determined according to the characteristics of the piezoelectric material.

Depositing an upper electrode metal layer on the second buffer layer 24, and patterning the piezoelectric material layer, the second buffer layer 24 and the upper electrode metal layer to form a piezoelectric layer 23 and an upper electrode 25; the material of the piezoelectric layer 23 may be a common piezoelectric material, which is a necessary film layer of the piezoelectric actuator, and the thickness thereof may be determined according to the design parameters of the piezoelectric actuator; the upper electrode 25 is a metal layer, the material of which can be determined according to the characteristics of the piezoelectric material, and is a necessary film layer of the piezoelectric actuator, and the thickness of which can be determined according to the design parameters of the piezoelectric actuator;

preferably, the piezoelectric layer 23, the second buffer layer 24, the upper electrode 25, and the first buffer layer 22 of the stress module 2 should cover a part of the sacrificial layer 14 in width, and the length is located within the scope of the sacrificial layer 14.

S10, depositing a dielectric layer 26 on the lower electrode 21, the upper electrode 25 and the upper cladding 17; dielectric layer 26 may be silicon dioxide or other insulating material;

the dielectric layer 26 is patterned to form a first contact hole 202 partially exposing the lower electrode 21 and a second contact hole 204 partially exposing the upper electrode 25.

And S11, depositing metal layers in the first contact hole 202 and the second contact hole 204 respectively to form corresponding electrode leads 206.

S12, depositing a protective layer 27; the protective layer 27 may be silicon dioxide or other insulating material.

Forming a trench penetrating the protective layer 27 over the sacrificial layer 14, exposing a portion of the sacrificial layer 14; the trench is greater than 1um from each of the first waveguide core 12, the second waveguide core 16, the lower electrode 21, and the electrode lead 206.

S13, removing the sacrificial layer 14 through the groove and wet etching, and forming a gap 104 between the first waveguide core 12 and the second waveguide core 16. The void 104 causes the first intermediate layer 13, the second intermediate layer 15, and the upper cladding layer 17 to collectively form a cantilever (plate) structure.

It is to be understood that the above-described embodiments of the present application are merely illustrative of or explanation of the principles of the present application and are in no way limiting of the application. Accordingly, any modification, equivalent replacement, improvement, etc. made without departing from the spirit and scope of the present application should be included in the scope of the present application. Furthermore, the appended claims are intended to cover all such changes and modifications that fall within the scope and boundary of the appended claims, or equivalents of such scope and boundary.

Claims (15)

1. An optical phase modulation device, comprising:

a substrate (10);

a first waveguide core (12) disposed on the substrate (10);

a second waveguide core (16) disposed in an upper cladding (17) above the first waveguide core (12), the first waveguide core (12) and the second waveguide core (16) having a variable gap (104) therebetween;

and the stress module (2) is arranged on the upper cladding (17) above the gap (104), the upper cladding (17) is deformed through the deformation of the stress module (2), and the gap (104) between the first waveguide core (12) and the second waveguide core (16) is enlarged or reduced through the deformation of the upper cladding (17).

2. An optical phase modulation device according to claim 1 wherein,

the upper cladding (17) is formed into a cantilever beam or cantilever plate structure with one end fixed and the other end suspended;

the second waveguide core (16) is formed in the suspended upper cladding (17), or at least a portion of the second waveguide core (16) is formed in the suspended upper cladding (17).

3. The optical phase modulation device according to claim 2, further comprising:

a thermal oxide layer (11) provided on the substrate (10);

a first intermediate layer (13) which is provided on the thermal oxide layer (11) and which covers the first waveguide core (12);

wherein the refractive index of the first waveguide core (12) is higher than the refractive index of the thermal oxide layer (11) and higher than the refractive index of the first intermediate layer (13).

4. An optical phase modulation device according to claim 2 or 3 and further comprising:

a second intermediate layer (15), a part of which is formed on the thermal oxide layer (11) or the first intermediate layer (13) and is formed into a cantilever beam or cantilever plate structure with one end fixed and the other end suspended, so that the second waveguide core (16) is formed on the second intermediate layer (15);

wherein the refractive index of the second waveguide core (16) is higher than the refractive index of the upper cladding layer (17) and higher than the refractive index of the second intermediate layer (15).

5. Optical phase modulation device according to claim 1, characterized in that the stress module (2) comprises:

a lower electrode (21);

a piezoelectric layer (23) provided on the lower electrode (21);

an upper electrode (25) provided on the piezoelectric layer (23);

wherein the piezoelectric layer (23) is deformed by a voltage difference applied to the lower electrode (21) and the upper electrode (25), the upper cladding layer (17) is deformed by the deformation of the piezoelectric layer (23), and the gap (104) between the first waveguide core (12) and the second waveguide core (16) is enlarged or reduced by the deformation of the upper cladding layer (17).

6. Optical phase modulation device according to claim 5, characterized in that the stress module (2) further comprises:

a dielectric layer (26) covering the upper electrode (25), the piezoelectric layer (23) and the lower electrode (21); the dielectric layer (26) is provided with a first contact hole (202) and a second contact hole (204); the first contact hole (202) is used for partially exposing the lower electrode (21); the second contact hole (204) is used for partially exposing the upper electrode (25);

a first buffer layer (22) provided between the lower electrode (21) and the piezoelectric layer (23);

a second buffer layer (24) provided between the piezoelectric layer (23) and the upper electrode (25);

an adhesive layer (20) provided between the upper cladding layer (17) and the first buffer layer (22).

7. Optical phase modulation device according to claim 1, characterized in that the stress module (2) comprises:

at least one thermal expansion layer sequentially arranged on the upper cladding layer (17);

a heater disposed on the thermal expansion layer;

wherein the coefficient of expansion of the thermal expansion layer is greater than the coefficient of expansion of the upper cladding layer (17), and the coefficient of expansion of the thermal expansion layer closer to the heater is greater than the coefficient of expansion of the thermal expansion layer farther from the heater; the heater heats the thermally-expansive layer, causing the thermally-expansive layer to thermally expand and deform, thereby changing the size of the void (104) between the first waveguide core (12) and the second waveguide core (16).

8. An optical phase modulation device according to any one of claims 1-7 wherein,

the first waveguide core (12) and the second waveguide core (16) are of a double-strip optical waveguide structure; the second waveguide core (16) is positioned right above the first waveguide core (12);

the first waveguide core (12) and the second waveguide core (16) each have a width that is less than the width of the void (104); the width of the first waveguide core (12) and the width of the second waveguide core (16) are the same or different;

the thickness of the first waveguide core (12) and the thickness of the second waveguide core (16) are the same or different;

the material of the first waveguide core (12) and the material of the second waveguide core (16) are the same or different.

9. A method of fabricating an optical phase modulation device, comprising:

providing a substrate (10);

-forming a first waveguide core (12) on the substrate (10);

depositing and patterning a sacrificial layer (14) over the first waveguide core (12), the patterned sacrificial layer (14) having a width greater than the width of the first waveguide core (12) below;

-forming a second waveguide core (16) on the sacrificial layer (14); the width of the second waveguide core (16) is smaller than the width of the patterned sacrificial layer (14);

forming an upper cladding layer (17) on the second waveguide core (16);

-forming a stress module (2) on the upper cladding (17);

etching away the sacrificial layer (14) to form a variable void (104) between the first waveguide core (12) and the second waveguide core (16);

wherein the upper cladding (17) is deformed by deformation of the stress module (2), and the gap (104) between the first waveguide core (12) and the second waveguide core (16) is enlarged or reduced by deformation of the upper cladding (17).

10. The method of manufacturing according to claim 9, characterized in that a first waveguide core (12) is formed on the substrate (10), in particular comprising:

-depositing a thermal oxide layer (11) on the substrate (10);

-forming a first waveguide core (12) on the thermal oxide layer (11);

depositing a sacrificial layer (14) on the first waveguide layer, comprising in particular:

depositing a first intermediate layer (13) on the thermal oxide layer (11) on which the first waveguide core (12) is formed, the thickness of the first intermediate layer (13) being greater than the thickness of the first waveguide core (12) so that the first intermediate layer (13) encapsulates the first waveguide core (12);

-depositing a sacrificial layer (14) on the first intermediate layer (13);

wherein the refractive index of the first waveguide core (12) is higher than the refractive index of the thermal oxide layer (11) and higher than the refractive index of the first intermediate layer (13).

11. The method of manufacturing according to claim 10, characterized in that a second waveguide core (16) is formed on the sacrificial layer (14), in particular comprising:

depositing a second intermediate layer (15) on the first intermediate layer (13) on which the sacrificial layer (14) is formed;

-forming a second waveguide core (16) on said second intermediate layer (15); -the second waveguide core (16) is formed over the sacrificial layer (14), or-at least a portion of the second waveguide core (16) is formed over the sacrificial layer (14);

wherein the refractive index of the second waveguide core (16) is higher than the refractive index of the upper cladding layer (17) and higher than the refractive index of the second intermediate layer (15).

12. The method of manufacturing according to claim 9, characterized in that the forming of the stress module (2) comprises:

depositing and patterning a lower electrode metal layer on the upper cladding layer (17) to form a lower electrode (21);

and depositing a piezoelectric material layer on the lower electrode (21), depositing an upper electrode metal layer on the piezoelectric material layer, and patterning the piezoelectric material layer and the upper electrode metal layer to form a piezoelectric layer (23) and an upper electrode (25), so that the stress module (2) formed after patterning partially covers the sacrificial layer (14) in the width direction and is positioned in the range of the sacrificial layer (14) in the length direction.

13. The method according to claim 12, wherein,

before the forming of the lower electrode (21), further comprising: depositing an adhesion layer (20) on the upper cladding layer (17); then, forming the lower electrode (21) specifically includes:

depositing and patterning a lower electrode metal layer on the adhesion layer (20) to form a lower electrode (21);

after the formation of the lower electrode (21), further comprising: depositing a first buffer layer (22) on the lower electrode (21); the forming of the piezoelectric layer (23) and the upper electrode (25) specifically includes:

depositing a piezoelectric material layer on a first buffer layer (22), depositing a second buffer layer (24) on the piezoelectric material layer, depositing an upper electrode metal layer on the second buffer layer (24), and patterning the piezoelectric material layer, the second buffer layer (24) and the upper electrode metal layer to form a piezoelectric layer (23) and an upper electrode (25);

after forming the upper electrode (25), further comprising:

depositing a dielectric layer (26) on the lower electrode (21), upper electrode (25) and upper cladding layer (17);

patterning the dielectric layer (26) to form a first contact hole (202) to partially expose the lower electrode (21), and a second contact hole (204) to partially expose the upper electrode (25);

a metal layer is deposited and patterned on the dielectric layer (26), and electrode leads of the stress module (2) are respectively formed at the first contact hole (202) and the second contact hole (204).

14. The method of manufacturing according to claim 9, the etching to remove the sacrificial layer (14), comprising:

forming a trench over the sacrificial layer (14) exposing a portion of the sacrificial layer (14);

the sacrificial layer (14) is etched away through the trench, forming the void (104).

15. The method of manufacturing according to claim 9, characterized in that the forming of the stress module (2) comprises:

forming at least one thermal expansion layer on the upper cladding layer (17);

forming a heater on the thermal expansion layer;

wherein the coefficient of expansion of the thermal expansion layer is greater than the coefficient of expansion of the upper cladding layer (17), and the coefficient of expansion of the thermal expansion layer closer to the heater is greater than the coefficient of expansion of the thermal expansion layer farther from the heater; the heater heats the thermally-expansive layer, causing the thermally-expansive layer to thermally expand and deform, thereby changing the size of the void (104) between the first waveguide core (12) and the second waveguide core (16).